So I finally got normal maps working (and they look fantastic!). My next quest is to get specular maps working. Doom3 specular maps are either RGBA or RGB textures, so my initial guess is to do something like this:

But, I think I've got a problem in that I don't know if the half-vector starts in object or eye space (I think eye space, which would mean I'm not actually putting it into tangent space). I'm also not sure if I'm applying the specular map correctly (I can't find any GLSL tutorials or non-grayscale tutorials at the moment). I'm also not sure of what to set the shininess factor to since it's not encoded in the specular map.
I guess I'm basically asking for any advice or links I can get. I don't see this being as hard to figure out as normal maps, I just don't know if I'm on exactly the right track yet.

It seems to work. I see a sort of gloss on the metalic sections of the models. I assume that's what I should be seeing? The gloss moves as I move, just as I would expect in the real world. It's really subtle though and I cranked the shininess up to 128. It's a cool effect, I just hope I'm doing it properly.